Magnetic switch actuator



June 1, 1965 w, |NDSAY 3,187,140

MAGNETIC SWITCH ACTUATOR Filed Oct. 2, 1961 4 Sheets-Sheet l a W IN VEN TOR.

WESLEY N. LINDSAY "Gi a/401i @044 his A 77' ORA/E Y rII'El l 4 Sheets-Sheet 2 W. N LINDSAY MAGNETIC SWITCH ACTUATOR June 1, 1965 Filed Oct. l2, 1961 INVENTOR.

14/5545) Al. LINDSAY mjf m3 AI'I'OflA/EY INVENTOR. W554 EY/V. L/NDSA Y his ATTORNEY 4 Sheets-Sheet 5 W N LINDSAY MAGNETIC ,SWITCH ACTUATOR June 1, 1965 Flled Oct 2, 1961 United States Patent 3,187,140 MAGNETIC SWITCH ACTUATOR Wesley N. Lindsay, San Jose, Calif assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed Oct. 2, 1961, Ser. No. 142,327 8 Claims. (Cl. 200-87) This invention relates to a magnetic switch actuator and more particularly to a device for actuating a vacuum switch by means of magnetic circuits.

One of the principal objects of the invention is the provision of a switch actuator for a vacuum switch which operates effectively under adverse conditions of vibration.

Another object of the invention is the provision of a switch actuator for holding a switch contact in either an open or closed position as desired and providing for rapid transfer from one to the other position at high speed with a minimum of inertial effects which might otherwise produce bouncing of the switch contacts.

Still another object of the invention is the provision of a switch actuator which operates to provide a synchronized opening and closing of two switch contacts as in a single pole double throw switch.

A still further object of the invention is the provision of a fast acting switch actuator which effectively holds the switch contacts in the desired position without the continuousexpenditure of power.

A further object of the invention is the provision of a switch actuator employing a permanent magnet which incorporates means for preventing demagnetization of the magnet.

The invention possesses other objects, some of which with the foregoing, will be brought out in the following description of the invention. I do not limit myself to the showing made by the said description, since I may adopt variant forms of the invention within the scope of the appended claims.

In the drawings:

FIG. 1 is a side elevation, partly broken away and in section of a combination of vacuum switch and actuator incorporating the invention.

FIG. 2 is a vertical section in a plane indicated by lines 2-2 of FIG. 1.

FIG. 3 is a rear elevation of the actuator showing the flux shunt.

FIG. 4 is a horizontal cross section of the actuator in a plane indicated by lines 4-4 of FIG. 1.

FIG. 5 is a vertical section in a plane indicated by lines 5-5 in FIG. 4 showing the armature in a neutral nonoperating position.

FIG. 6 is a simplified semischematic perspective of the actuator and associated switch contacts.

.Broadly considered the actuator of the present invention is adapted to be employed with a vacuum switch of the single pole double throw type which includes a pair of shafts respectively connected at one of their corresponding ends to a pair of switch contacts and at their other ends to a balanced switch armature. The armature is pivotally supported for swinging ineither direction about a horizontal axis and is interposed between opposed pole pieces of a permanent magnet with said shaft-s connected to its oppo site ends. By energizing a coil on said armature the same may be swung in either direction into engagement with the pole pieces to actuate both switch contacts simultaneously. Upon such actuation the current in the coil may be shut off, The armature, and therefore the switch contacts, are held in one of the desired positions by permanent magnet forces. Revers-ing the flow of current in flux producing coil-s of the armature causes the armature to be swung in a reverse direction to the other desired position.

Means are provided for accurately balancing the switch Patented June 1 1965 armature so that the energy expended in actuating it is a minimum. However, the actuating structure is arranged so that the armature is securely held in the particular position to which it is moved. In addition, means is also provided for adjusting the holding force of the magnet circuit to obtain the particular characteristics required.

The invention is adapted to be employed in conjunction with a vacuum switch such as generally designated 1 in FIGS. 1, 2. This switch 1 is the same as that disclosed in detail in application Serial No. 852,105, filed November 10, 1959, now abandoned, but for the purpose of the present invention it is sufiicient to note that the switch comprises a central fixed contact 2 and a pair of outer fixed contacts 3, 4 respectively. As best seen in FIG. 6 a circuit is completed between contacts 2, 3 by means of a vertically movable shorting blade 5 while a circuit is completed through contacts 2, 4 by a similar shorting blade 6. As will be noted from the following description one shorting blade or the other is in contact with its respective contacts in any one position of the switch.

Shorting blades 5, 6 are insulated from and connected by means of shafts 7, 8 with the opposite ends of an elongated sof-t iron armature generally designated 10 in FIG. 6. Armature 10 is formed of laminated iron and is horizontally disposed and is swingably supported intermediate its ends on a central pivot 11 so that the structure that includes the armature 10, shafts 7, 8 and shorting blades 5, 6 is perfectly balanced. Shafts 7, 8 are pivotally connected .to the armature by pins 18, 19.

Referring now to FIG. 1, the actuator housing generally designated 12 includes a horizontally disposed base plate 13 which is fixedly secured to the housing of switch 1 by means of connector plates 14. Extending between switch 1 and base plate 13 are a pair of cylindrical tubes 15, 16 which serve to house the shafts 7, 8 respectively. Said tubes 15, 16 are integrally and hermetically sealed to the switch housing and a pair of bellows 20 are hermetically connected at their upper ends to the underside of base plate 13 and at their lower ends to shafts 7, 8 respectively.

It is apparent that the atmospheric pressure against the bellows vacuum seals would be exerted at all times through shafts 7, 8 and armature 10 on the central pivot 11 if not counterbalanced. To balance the force of the atmosphere and any spring pressure exerted by the bellows, springs 21, 22 are provided on shafts 7, 8 respectively. These springs bear against the base plate 13 at their lower ends and at their upper ends abut washers 23, 24 which in turn are adjustably positioned relative to shafts 7, 8 by nuts 25, 26 respectively. By proper selection of springs 21, 22 and by adjustment of nuts 25, 26 the armature 10 may be perfectly balanced in a horizontal position with no loading on pivot 11, assuming no external forces acting on the above described assembly.

At this point it may also be noted that by proper selection of the spring constant of springs '21, 22 the natural frequency of the armature and the elements carried thereby may be predetermined so that the period of vibration equals twice the desired actuation time to open one contact and close the other; each actuation of the switch corre sponding to a one-half cycle of the springs as the latter undergo simple harmonic motion. As will be seen later on the work required to transfer the switch from one position to the other is only that required to overcome the frictional losses of the system.

The means for energizing the actuator includes a pair of permanent magnets 30, 31 (FIG. 4) which are held between a pair of upper and lower retainer plates 32, 33 which in turn are secured by bolts 35, to posts 36 carried by base plate 13. Secured by bolts 40, 41 to the upper retainer plate 62 are a pair of pole pieces 42, 43 respectively. The holes 44, 45 (FIG. 5) in pole pieces 42, 43

3 l for receiving bolts 40, 31 are somewhat larger in diameter than the bolts to permit said pole pieces to be adjusted slightly as desired. Similarly, a pair of pole pieces 43, 49 are secured by bolts 50, 51 to lower retainer plate 33 and a pair of oversize holes 52, 53 (FIG. are provided in pole pieces 48, 49 for this purpose. Pole pieces 42, 43 may be regarded as a single pole piece as may pole pieces 48, 49 and such an arrangement is contemplated by this invention and it is quite workable. However, the use of four pole pieces simplifies adjustment.

As best seen in FIG. 5 the pole pieces 42, 43, 48, 49 are positioned on permanent magnet retainer plates 32, 33 so as to be engaged by armature when the latter swings from its neutral position of FIG. 5. By means of bolts 41, 50 the pole pieces 43, 48 may be adjusted so as to engage the upper and lower sides respectively of armature -19 when the latter is swung to a position in which shorting blade 5 (FIG. 6) engages contacts 2, 3. Similarly, by

means of bolts 40, 51 pole pieces 42, 4? may be adjusted so as to engage the upper and lower sides of the armature as shorting plate 6 engages contacts 2, 4.

The pivot 11 for armature 10 consists of a pair of pins 60, 61 (FIG. 4) which are secured to supporting blocks 62, 63 respectively. Block 62 is secured by means of screws .64, 6 5 (FIG. 3) to upper and lower retainer plates 32, 33 respectively, (FIG. 3), and block 63 is secured to lower retainer plate '33 by screws 66 (FIG. 4). Pins 60,

.61 do not engage the metal of armature 10 but are received within complementarily formed recesses 69 in a hard plastic coil encapsulant 70 ('FIG. 4) which serves as a housing for a coil 71 surrounding armature 10. Although asingle coil may be employed to energize armature 10 it is more practical .to provide a pair of coils, as indicated schematically in FIG. 6, so as to create magnetomotive forces of opposed polarity. In such a case two single pole single throw switches 72, '73 may be employed to energize the coils thus obviating a complicated switching system.

At this point, the operation of the actuator can be described. The upper pole pieces 42, 43 are at a magnetic potential different from that of the lower pole pieces 48, 49. If it is assumed that the armature is tilted to engage pole pieces 43, 48 and close shorting blade 5 it is apparent that the flux carried by pole pieces 43, 48 holds the armature firmly in its tilted position. If the current in coil 71 is then caused to flow in a direction to create a flux in the armature which is opposite to that created by the permanent magnets 3d, 31, and if the magnitude of the net flux becomes less than that corresponding to the force required to offset the force exerted by springs 21, 22 tending to return the armature to neutral position, the armature will start to move. Whereas the flux from the coil 71 opposes the flux from the permanent magnets which flows through pole pieces 43, 48 it adds to the permanent magnet tlux tending to flow through'the armature from the pole pieces 42, 49. The coil flux thus causes the armature to swing to a position in engagement with pole pieces 42, 49. When the coil is deenergized the permanent magnet dlux holds the armature securely against pole pieces 42, 49. A reversal of polarity of the voltage to the coil returns the armature to its opposite position in engagement with pole pieces 43, 48.

An important feature of the invention resides in the fact that each of the springs 21, 22 tends to move from its extreme compressed condition to its expanded condition (as limited by the associated structure) with simple harmonic motion. The energy required to elfect transfer of the switch as above described is therefore supplied almost entirely by the springs and the associated bellows; the energy provided by coil 71 being required only to overcome frictional losses in the system.

It is essential to successful repeated operation of the above described actuator that the mechanism and magnetic circuit be designed so as to eliminate any tendency for the permanent magnets 30, 31 to become demagnel tized. To this end it is desirable to provide means for preventing the flux density in magnets 30, 31 from dropping below a point corresponding to the flux density on the demagnetization curve at which they become demagnetized.

Referring now to 'FIGS. 2, 3 a pair of elongated shunt plates 74-, 75 are positioned horizontally along the underside of upper retainer plate 32 and along the upper side of lower retainer plate 33 respectively and are secured to block 62 centrally of their length by means of screws 76, 77 (FIG. 3). The adjacent edges of shunt plates 74, 75 are spaced apart to provide a flux path of a sufliciently low predetermined reluctance regardless of the effect of coil 71 and armature 10. A spacer 78 of nonmagnetic material is interposed between shunt plates 74, 75. Parts 74, 75 and 78 thus comprise the stationary part of the magnetic circuit while the armature 10 comprises the moving part.

The exact design of the magnetic circuit may be arrived at by determining first the required flux in the pole pieces 42, 43, 48, '49 to provide the desired predetermined holding force to suit the conditions under which theactuator must operate. Once this flux is determined and a trial selection of magnetic material made, the reluctance of the fixed shunt portion of the magnetic circuit may be adjusted to a value to prevent demagnetization of the magnets 30, 31 even if the armature 10 were completely removed from the assembly. The required cross section and length of the magnet are then determined by known methods to provide the required magnetomotive force and flux. The number of ampere turns in the coil 71 may likewise be determined by solution of the circuit. Motion of the armature away from one pair of the pole pieces starts when the magnetic force developed in the pole pieces is slightly less than the spring force tending to pull the armature into its neutral position.

The above described structure is extremely reliable since the opening and closing of the two shorting blades is synchronized. Furthermore the use of the springs as above described insures a rapid motion of the shorting blades and at the same time the natural simple harmonic motion of the springs results in the shorting blades engaging the fixed contacts at a low velocity thereby minimizing any tendency of the switch contacts to bounce.

As noted above the actuator is particularly efiicient when used under conditions of vibration since a strong magnetic latching is effected between the armature and its associated pole pieces Without the expenditure of power.

I claim:

1. An actuator for a switch having a switch element and a shaft supporting said switch element for movement of the latter to one or the other of two positions, comprising: an armature supported for oscillation about a pivot and connected at one of its ends to said shaft, a permanent magnet including a pair of pole pieces of opposite polarity on opposite sides respectively of said one end, resilient means for holding said armature in an intermediate position between and spaced from said pole pieces and for yieldably resisting movement of said one end toward either of said pole pieces, means on said armature for establishing a flux in said armature having a direction opposite to the flux created by said permanent magnet whereby said armature is swung about said pivot to a position with said one end in engagement with one of said pole pieces and with said switch element in one of said two positions whereby said armature is held in said last mentioned position by the magnetic force of said one pole piece against the force of said resilient means when said flux establishing means is deenergized.

3. The combination according to claim 2 in which the natural period of oscillation of the armature and its associated moving parts is equal to twice the time taken for said armature to swing from said pole piece to the other pole piece.

4. The combination according to claim 1, in which a shunt including a gap of predetermined width is provided on said permanent magnet to establish a flux path other than the flux path through said pole pieces to prevent demagnetization of said permanent magnet by the opposing flux established in said armature.

5. An actuator for a switch having a pair of switch elements each adapted to move from one to the other of two positions comprising; an elongated armature pivotally supported intermediate its opposite ends, a pair of shafts connecting the opposite ends of said armature with said switch elements respectively, resilient means operatively connected with said armature for urging the same to an intermediate position in which said switch elements are each positioned intermediate said two positions, a permanent magnet including a pair of opposed pole pieces having opposite polarity, said pole pieces being arranged on opposite sides of said armature whereby each end of said armature engages one of said pole pieces when said armature is swung in one direction and engages the other of said pole pieces when swung in the opposite direction, and whereby the magnetic force of said pole pieces holds said armature in engagement with said pole pieces when said armature is tilted from said intermediate position into engagement with said pole pieces at its opposite ends, means on the armature for establishing a flux in said armature having a direction opposite to the direction of the flux created by said permanent magnet whereby said magnetic force is reduced to permit said resilient means to swing said armature from the holding pole pieces toward said intermediate position.

6. The combination according to claim 5 in which the natural period of oscillation of the armature and its associated moving parts is equal to twice the time taken to move said switch element from one to the other of said two positions,

7. The combination according to claim 5 in which a shunt including a gap of predetermined width is provided on said permanent magnet to establish a flux path other than the flux path through said pole pieces to prevent demagnetization of said permanent magnet by the opposing flux established in said armature.

8. In combination with a vacuum switch that includes a pair of switch operating shafts extending outwardly from a vacuumized housing and in which a pair of bellows are hermetically sealed at one of their corresponding ends to said shafts respectively and fixedly secured relative to said housing at the other of their corresponding ends, an actuator for moving said shafts between two predetermined positions comprising: an elongated armature outside of said housing swingably supported on a pivot intermediate its ends and connected at its opposite ends to said shafts, springs operatively connected with the opposite ends of said armature for normally urging said armature to a position with said shafts intermediate said predetermined positions, said springs being stressed to offset the force of the atmosphere on said bellows and the resiliency of said bellows to minimize the loading on said pivot by said armature.

References Cited by the Examiner UNITED STATES PATENTS 931,242 8/09 Williams et al 200-93 2,166,327 7/39 Rypinski et al 200-93 2,198,781 4/40 Mample 200-87 2,238,913 4/41 Miller 200-93 2,398,681 4/46 Weber 200-87 2,718,614 9/55 Gamble 317-171 2,892,055 6/59 Wantosch 200-93 2,906,841 9/59 Jennings 200-144 2,951,134 8/60 Lazich 200-87 2,997,560 8/ 61 Callaway 200-93 BERNARD A. GILHEANY, Primary Examiner. MAX L. LEVY, ROBERT K. SCHAEFER, Examiners. 

1. AN ACTUATOR FOR A SWITCH HAVING A SWITCH ELEMENT AND A SHAFT SUPPORTING SAID SWITCH ELEMENT FOR MOVEMENT OF THE LATTER TO ONE OF THE OTHER OT TWO POSITIONS, COMPRISING: AN ARMATURE SUPPORTED FOR OSCILLATION ABOUT A PIVOT AND CONNECTED AT ONE OF ITS ENDS TO SAID SHAFT, A PERMANENT MAGNET INCLUDING A PAIR OF POLE PIECES OF OPPOSITE POLARITY ON OPPOSITE SIDES RESPECTIVELY OF SAID ONE END, RESILIENT MEANS FOR HOLDING SAID ARMATURE IN AN INTERMEDIATE POSITION BETWEEN AND SPACED FROM SAID POLE PIECES AND FOR YIELDABLY RESISTING MOVEMENT OF SAID ONE END TOWARD EITHER OF SAID POLE PIECES, MEANS ON SAID ARMATURE FOR ESTABLISHING A FLUX IN SAID ARMATURE HAVING A DIRECTION OPPOSITE TO THE FLUX CREATED BY SAID PERMANENT MAGNET WHEREBY SAID ARMATURE IS SWUNG ABOUT SAID PIVOT TO A POSITION WITH SAID ONE END IN ENGAGEMENT WITH ONE OF SAID POLE PIECES AND WITH SAID SWITCH ELEMENT IN ONE OF SAID TWO POSITIONS WHEREBY SAID ARMATURE IS HELD IN SAID LAST MENTIONED POSITION BY THE MAGNETIC FORCE OF SAID ONE POLE PIECE AGAINST THE FORCE OF SAID RESILIENT MEANS WHEN SAID FLUX ESTABLISHING MEANS IN DEENERGIZED. 